EVALUATION OF SOME 5-PYRAZOLONE-BASED COPPER(II) COMPLEXES AS CATALYSTS FOR THE OXIDATION OF <i>trans</i>-STILBENE
Keywords:copper(II) complexes, 5-pyrazolone, trans-stilbene oxide, catalytic oxidation, epoxidation, sonochemistry
AbstractThe catalytic properties of the azo- and bisazo-5-pyrazolone-based three copper(II) complexes have been studied. Heating under reflux with or without ultrasonic irradiation was applied for the different equivalent amounts of three copper(II) catalysts (0.6 and 1.0 mol %) in ethyl acetate. It has been shown that all pyrazolone-based copper(II) complexes are active for catalytic oxidation of trans-stilbene in the presence of tert-butyl hydroperoxide as the oxidant, providing high selectivity and good conversion values. Heating was applied to the different solvents: chloroform, tetrahydrofuran, N,N-dimethylformamide, and dioxane. All catalysts can be safely used near to the boiling point of the oxidant without decomposition and the efficacy of ethyl acetate under conventional heating and heating–ultrasonic conditions has been determined. Heating–ultrasonic conditions and 1.0 mol % of catalysts gave higher conversion than conventional heating and 0.6 mol % of catalysts. A mechanism is proposed for the catalytic oxidation of trans-stilbene with tert-butyl hydroperoxide.